Control of Surface Plasmon Resonance in Silver Nanocubes by CEP-Locked Laser Pulse

Abstract

Localized surface plasmon resonance (LSPR) of metal nanoparticles has attracted increasing attention in surface-enhanced Raman scattering, chemical and biological sensing applications. In this article, we calculate the optical extinction spectra of a silver nanocube driven by an ultrashort carrier envelope phase (CEP)-locked laser pulse. Five LSPR modes are clearly excited in the optical spectra. We analyze the physical origin of each mode from the charge distribution on different parts of the cubic particle and the dipole and quadrupole excitation features at the LSPR peaks. The charge distribution follows a simple rule that when the charge concentrates from the face to the corners of the cubic particle, the resonant wavelength red-shifts. Then we modulate the LSPR spectra by changing CEP. The results show that CEP has selective plasmon mode excitation functionality and can act as a novel modulation role on LSPR modes. Our work suggests a novel means to regulate LSPR modes and the corresponding optical properties of metal nanoparticles via various freedoms of controlled optical field, which can be useful for optimized applications in chemical and biological sensors, single molecule detection, and so on.

Creating 3D Nanoparticle Structural Space via Data Augmentation to Bidirectionally Predict Nanoparticle Mixture's Purity, Size, and Shape from Extinction Spectra

“…Generally, the LSPR position is the most sensitive to structural parameter variations due to pronounced electromagnetic retardation effects, where they redshift with increasing NP volumes which is related closely to the size and shape of the NPs (Figure 4B). [1a,7b,14] The FWHMs increase due to the volume effect and increased radiative damping in NPs of various shapes present in the NP mixture [7b] . In our case, we observe that the peak position of LSPR 1, 2, 4, and 5 belonging to Ag NCs, are the most instrumental in size predictions.…”

“…The LR model's autonomous feature ranking elucidates that the two higher‐order LSPR modes at ~300–450 nm, originating from the localized polarization charges at Ag NC′s corners and edges are the most critical input features driving all three structural parameters predictions [7a,b] . Such information is unprecedented and previously overlooked, given that the primary dipole and quadrupole LSPR modes at ~510 and ~640 nm are widely accepted as leading indicators of NP structural parameters [7a,b,8] . Our accurate and rapid (<30 s) approach offers insights into the complex optical response of heterogeneous NP systems and enables complete ML closed‐loop control in hybrid Ag NC synthesis‐characterization platforms, allowing real‐time monitoring of unpurified NPs during synthesis.…”

Creating 3D Nanoparticle Structural Space via Data Augmentation to Bidirectionally Predict Nanoparticle Mixture's Purity, Size, and Shape from Extinction Spectra

“…This observation corroborates well with our EM findings, whereby Ag NSs and NWs are the major impurities present in our as‐synthesized Ag NC solutions, indicating that the spectral intensities at these two regions can be used to evaluate the purity of the NP mixture. (Figure 1Aii) Next, in samples where the Ag NC′s size increases from 95–135 nm while their purity and corner radii remain at 90 % and 10 nm respectively, we note an increase in dipolar and quadrupolar LSPR modes of Ag NCs as both peaks broaden and redshift from 490 to ~520 nm and 620 to ~720 nm, respectively (Figure 1Di–iii; Figure S1) [7a,b, 9] . Finally, when assessing Ag NCs samples with increasing the corner radius of curvature from 7–11 nm while their purity and size remain constant at 90 % and 120 nm, we observe distinctive increases in the FWHM of both the quadrupolar and dipolar LSPR peaks from 50 to 100 nm and 180 to 300 nm (Figure 1Ei–iii; Figure S1).…”

“…Finally, the most critical peak attributes for Ag NC shape prediction are LSPR 1 and 2 positions (Figure 4C). This is because the nodes of the charge distribution are located at the cube corners, therefore they are expected to be susceptible to the exact Ag NC corner shape [7a,b] . Furthermore, the 342–386 nm and 523–581 nm spectral regions, lying at the respective intersections of LSPR 1–2 and LSPR 4–5, are also highly ranked, indicating a relationship between the shape and these peaks’ FWHM (Figure 4C).…”

“…Beyond predictions, we use the 3D NP structural space for data‐driven knowledge discovery. The LR model's autonomous feature ranking elucidates that the two higher‐order LSPR modes at ~300–450 nm, originating from the localized polarization charges at Ag NC′s corners and edges are the most critical input features driving all three structural parameters predictions [7a,b] . Such information is unprecedented and previously overlooked, given that the primary dipole and quadrupole LSPR modes at ~510 and ~640 nm are widely accepted as leading indicators of NP structural parameters [7a,b,8] .…”